SU822291A1 - Photoelectric converter - Google Patents

Description

The invention relates to optoelectronics and can be used in high-speed optical information processing systems, in particular in holographic storage devices. Known photoelectric semiconductor converters on photodiodes l and 2. Their disadvantages are 1 mc low threshold photosensitivity (10 j / element) and low speed. A photoelectric semiconductor converter is known, which is an integrated matrix whose cell has a two-emitter phototransistor. Single-type emitters of cell transistors are connected by mutually perpendicular tires 3. The disadvantage of this photoconverter is a long transient process when switching weak light signals (much more than 1 µs) As a result, at high frequencies this device does not allow a sensitivity higher than 10 10 j / element In addition, sensitivity is limited by interference from control signals and dark leakage current, which is strongly dependent on temperature, doubling as it increases by. Thus, the disadvantages The specified photovoltaic converter is a low speed and low threshold sensitivity and a narrow temperature range. Modern optical information processing systems require high sensitivity of a 1CG-10 J photocell / element at a speed of 10 Hz, in a wide temperature range (-60) - (+ 80С). of the invention is an increase in speed and threshold photosensitivity in the extended temperature range. The goal is achieved by the fact that in a photoelectric converter containing two earwire trinzister, the first of the emitters of which are connected to the control bus, the second of the emitters - with the corresponding differential readout buses, and the collectors - with the displacement bus, and the power bus, both two-emitter transistors are injection and their injectors are connected to

The power bus, moreover, one of the transistors is enclosed in an opaque coating.

The injector creates an optimal operating mode of the photoconverter, due to which its speed increases by 3-4 times. In this case, however, the threshold sensitivity of the photoconverter is deteriorated due to the increased dark currents. In general, sensitivity is limited by interference from control signals of dark leakage currents through pn junctions and dark currents caused by an injector. The use of identical semiconductor devices in each cell with dimming one of them and connecting the outputs to a differential amplifier allows one to compensate for all the mentioned interferences, while maintaining speed. Interferences associated with temperature changes are also compensated for, as the cell devices are the same and under the same conditions.

Figure 1 shows the electrical circuit of the proposed photoelectric converter; 2, the construction of one of the embodiments of the device.

The photoelectric converter contains bus 1 cm, two identical photosensitive semiconductor structures, for example, phototransistors 2 and 3. Light affects the phototransistor 2 cells, and the phototransistor 3 is protected by an opaque coating. Phototransistors are two-emitter cells, pnp type with common collector 4. Control signals are sent to their bases 5 through a capacitance of 6 pn-junctions formed by the base and emitter 7. The emitters 8 of transistors 2 and 3 belonging to a specific column are connected to corresponding differential readout tires 9. As an injector providing the operating mode of large pn-junction currents (hence the mode of small constant times), each device uses a pnp type transistor formed by the substrate 10 (emitter), the epitaxial layer of the collector 4 (base) and base 5 npp transistor (collector). The device has a control bus 11 and a power bus 12.

Both phototransistors of each cell operate dynamically with charge accumulation. The control signals on the control bus 11 are fed to the bases of the phototransistors 5 through the barrier capacitances of the emitter junctions 7. They charge the barrier capacitances of the 6 phototransistors, which in the pause between the control pulses are discharged by the photocurrent, the dark leakage current and the current generator. Obviously, noise signals and dark currents are the same for a number of integrated phototransistors of the integrated circuit; are compensated at the differential amplifier, and a signal proportional to the illumination is realized at the output of the amplifier. The injectors discharge partially the barrier capacitances b and, thus, ensure the output of the phototransistors during a pulse survey to a high current mode corresponding to a small constant time. The injectors can discharge capacitances b either constant (as shown in FIG. 2) or pulsed current in the pauses between the pulses of the interrogation generator, providing a hole charge 4-10 times higher than the maximum charge of the photocurrent.

The proposed phototransducer favorably differs from the known

that it provides a HIGH threshold

-f4 -1b sensitivity (10 -10J / cell), wide temperature range (-60) - (+ 80 ° s) and high speed (10 s). This expands the field of application of the proposed photoconverter in comparison with the known one.

Claims (3)

1. A photoelectric converter containing two two-emitter transistors, the first of which emitters are connected to the control bus, the second of the emitters to the corresponding differential readout buses, and the collectors to the bias bus, and the power bus, which is different in that with the aim of increasing speed and transducer sensitivities, two emitter transistors are injection molded and their injectors are connected to the power rail. 2. The converter according to claim 1, characterized in that one of the two emitter transistors is enclosed in an opaque coating Sources of information taken into account in the examination 1. US patent 3,614,775 cl. 340-173, 1971. 2. US patent number 3689900, CL.340-137, 1972. 3. Tujctsu Sientific Technical Journal, 1972, September, p.l37151 (prototype). Phi.